This invention relates to a commodity key as used in a computing scale and labeling system, such as shown in U.S. Pat. No. 3,961,747 issued June 8, 1976 and No. 3,989,929 issued Nov. 2, 1976 to Hobart Corporation, assignee of this application. The commodity key shown in those patents is typical of prior art devices which include a printing area, usually a raised type rubber printing plate, together with a code area which bears a unique code identifying in some machine readable form the commodity which is identified in human readable form on the printing area.
In the past, the code has been provided by drilling a pattern of holes arranged in a unique pattern within several rows on a key having a metal body. The user purchases the key from a supplier, and the code already is formed in the key. The key is used by inserting it into an appropriate receiving slot in a computing scale system, and the code area is read by a plurality of light sensitive devices such as photodiodes upon which a light source is directed selectively by the pattern of holes through the key. It has been found, however, desirable to have the ability to encode special code information into the commodity key, and it is generally desirable to provide the user with blank keys which he can encode appropriately on site, and to which he can attach the corresponding printing plate or patch. Such a key must, however, be durable enough to withstand the handling, such as insertion and removal in the scale system, encountered in every day use.